Introduction to Programming in C

📘 Loops in C (for, while, do-while)

In programming, loops are used to execute a block of code multiple times until a specified condition is met. C provides three main types of loops: for, while, and do-while. Mastering loops allows you to build powerful and efficient logic for repetitive tasks.

🔁 Why Use Loops?

• To avoid writing repetitive code
• To iterate through arrays and collections
• To run code based on conditions until it’s false
• To automate repetitive tasks like printing patterns, summing numbers, etc.

🔹 The for Loop

Used when the number of iterations is known beforehand.

for (int i = 1; i <= 5; i++) {
    printf("Iteration %d\n", i);
}

This will print:

Iteration 1
Iteration 2
Iteration 3
Iteration 4
Iteration 5

🔹 The while Loop

Used when the number of iterations is not known and depends on a condition.

int i = 1;
while (i <= 5) {
    printf("Value = %d\n", i);
    i++;
}

🔹 The do-while Loop

Executes the block at least once, then checks the condition.

int i = 1;
do {
    printf("i = %d\n", i);
    i++;
} while (i <= 5);

💡 Key Differences

📘 Nested Loops

A loop inside another loop. Used for pattern printing and 2D arrays.

for (int i = 1; i <= 3; i++) {
    for (int j = 1; j <= 3; j++) {
        printf("%d ", j);
    }
    printf("\n");
}

🔂 Infinite Loop Example

while (1) {
    printf("This will run forever unless you break it.\n");
}

⚠️ Loop Control Statements

• break; – exit from the loop immediately
• continue; – skip current iteration and go to the next

for (int i = 1; i <= 5; i++) {
    if (i == 3) continue;
    printf("%d ", i);
}
// Output: 1 2 4 5

📚 Real-Life Example (UdaanPath)

Suppose UdaanPath wants to list top 10 trending courses on the homepage:

for (int i = 0; i < 10; i++) {
    printf("Course #%d: Learn Programming\n", i + 1);
}

📝 Practice Tasks

1. Print all numbers from 1 to 100 using for, while, and do-while.
2. Print multiplication table of a number using loops.
3. Write a program to calculate the factorial of a number using a loop.
4. Print a pattern like:
   1
   1 2
   1 2 3
   ... up to N rows using nested loops.

📌 Summary

• Loops are essential for executing repetitive tasks efficiently.
• Choose for for known iterations, while for conditional, and do-while when code must run at least once.
• Loop control statements like break and continue provide more control within loops.

✅ Coming Next

In the next chapter, we’ll explore Functions in C — how to declare, define, and use functions, including recursion.